THE HUMAN PLACENTAL-LACTOGEN GENES - STRUCTURE, FUNCTION, EVOLUTION AND TRANSCRIPTIONAL REGULATION

The placenta is an important source of a diverse group of hormones, cytokines, and growth factors necessary for continuation of pregnancy. Due to its continued growth and differentiation during gestation, the placenta represents a unique organ for the study of hormonal genes during development. The production of one hormone in particular, placental lactogen (PL), also called chorionic somatomammotropin (CS), reflects the development of the placenta as blood PL levels rise throughout pregnancy and reach a peak at term. Human PL (hPL) is a member of a closely related gene family that includes human GH (hGH) and human PRL (hPRL). Although these genes are highly similar and have evolved from a common precursor, they have dramatically different physiological functions and regulatory mechanisms. Recently, advances have been made in understanding the regulation of hPL production and its physiological significance. In this review we discuss the various physiological actions of hPL during pregnancy, the evolution and structure of hPL genes, and the tissue-specific regulation of hPL gene expression. © 1991 by The Endocrine Society.